30mm Venturi, for 40 Dcoe Weber Carburetors

OVERVIEW

When it comes to fine-tuning your high-performance air-cooled engine, the venturioften referred to as the "choke"is the most critical component for determining the velocity and volume of air entering your combustion chamber. This EMPI 30mm Main Venturi is precision-engineered specifically for the iconic 40 DCOE Weber carburetor, as well as high-quality clones. By choosing a 30mm diameter, you are optimizing your intake signal for superior low-to-mid-range throttle response. In the world of side-draft carburetion, velocity is king; a slightly smaller venturi like the 30mm creates a stronger vacuum signal over the auxiliary venturi, which allows the main circuit to activate earlier and more smoothly. This eliminates the dreaded "flat spot" often found in oversized setups, making it the perfect choice for street-driven Beetles, Ghias, or Type 3s that require crisp off-the-line acceleration and manageable drivability in traffic.

At Appletree Automotive, we know that "one size fits all" doesn''t apply to performance VW engines. This 30mm venturi is manufactured by EMPI to exacting tolerances, ensuring a snug fit within the carburetor barrel to prevent air leaks that could lead to an inconsistent idle or lean spikes. Whether you are running a spirited 1776cc or a torquey 1914cc engine, swapping to a 30mm venturi allows you to tailor the power band to your specific driving style. If you find your current 40 DCOE setup feels "soggy" or unresponsive at lower RPMs, upgrading to these precision-cast venturis will restore the snap and urgency your air-cooled powerplant deserves. Don''t settle for "good enough" tuning when you can achieve perfection with the right internal components designed for the rigors of the road and the track.

FITMENT

This 30mm Venturi is designed for use with the following applications utilizing 40 DCOE Side-Draft Carburetors:

• Volkswagen Beetle: All years (with 40 DCOE side-draft conversion).
• Volkswagen Karmann Ghia: 1956-1974 (with 40 DCOE side-draft conversion).
• Volkswagen Bus / Type 2: 1950-1979 (with 40 DCOE side-draft conversion).
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1961-1973.
• Porsche 356 & 912: Utilizing 40 DCOE carburetor upgrades.
• Universal Applications: Fits any genuine Weber 40 DCOE, EMPI 40 DCOE, or Fajs 40 DCOE carburetor series.

SPECS

The following technical specifications ensure compatibility and performance for your Weber tuning needs:

• Carburetor Series: 40 DCOE (Side-Draft).
• Internal Diameter: 30mm.
• Component Type: Main Venturi (Choke).
• Material: High-grade precision-cast zinc alloy.
• Finish: Machined smooth for laminar airflow.
• Manufacturer: EMPI.
• Part Number: 43-5602-0.
• Quantity: Sold individually (two required per dual-throat carburetor).

PRO TIPS

Tip 1: The Golden Rule of Venturi Sizing

Choosing the right venturi is a balancing act between air speed and total volume. As a general rule of thumb for street-driven air-cooled VWs, your venturi size should be approximately 3mm to 4mm smaller than the intake valve diameter, or sized to maintain high velocity at the RPM range where you spend 80% of your time. The 30mm size is exceptional for engines between 1600cc and 1914cc that prioritize "stoplight-to-stoplight" torque over absolute peak horsepower at 7,000 RPM. If your engine feels sluggish or bogs when you floor it at 2,500 RPM, your current venturis are likely too large; dropping down to this 30mm size will significantly sharpen the engine''s "bite" and improve overall fuel atomization.

Tip 2: Synchronize Your Jetting Changes

Whenever you change the venturi size in your Weber 40 DCOE, you MUST re-evaluate your jetting. Because a 30mm venturi increases the air velocity compared to a 32mm or 34mm, it will pull more fuel through the main circuit for a given volume of air. Typically, when you decrease the venturi size, you may need to slightly reduce your main jet size or increase your air corrector size to maintain the ideal air-fuel ratio. Always perform a spark plug reading or use a wideband O2 sensor after installation to ensure your engine isn''t running too rich or too lean in the transition from the idle circuit to the main circuit.

Tip 3: Inspection and Seating During Installation

Before sliding your new 30mm venturis into the carburetor bodies, inspect the outer mating surfaces for any tiny casting flashes or burrs. Even a microscopic imperfection can prevent the venturi from seating perfectly square within the barrel. When installing, ensure the venturi is fully seated against the internal stop before tightening the intake trumpet or the venturi retaining screw. If the venturi is loose or misaligned, it can cause "whistling" noises and turbulent air, which disrupts the fuel signal from the auxiliary venturi. Use a small amount of light oil on the outer rim to help it slide into place smoothly without galling the aluminum carburetor body.